A/C Post Heater Sensor #2 Circuit Short to Ground
The A/C heater sensor after the evaporator is detecting a short circuit to ground, similar to a wire touching metal when it shouldn't. The ECU can't properly read the sensor's signal because the electrical path is broken.
The ECU monitors the A/C post-heater temperature sensor's voltage signal to regulate cabin climate. When the sensor shorts to ground, the ECU detects an abnormally low voltage (near 0V) that falls outside acceptable operating range, triggering the fault code.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Sensor voltage | 0.5-4.5V (proportional to temperature) | <0.1V or short to ground detected |
| Temperature reading | -40°C to 125°C range | Unrealistic or stuck reading |
Code B2429 is a low-severity fault. Your vehicle is generally safe to drive to a workshop for diagnosis. However, do not ignore it indefinitely — low-severity codes often indicate developing problems that become expensive if neglected. Book a diagnostic appointment within 2–4 weeks. If you notice any additional symptoms (rough running, power loss, unusual smells), treat it as higher priority.
Once the fault is repaired, B2429 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.